Labels

ABSTRACT

There is described a label comprising a self supporting sheet of a biopolymer (preferably cellulose (e.g. regenerated cellulose), cellulose acetate and/or PLA) said sheet being substantially transparent to visible light when uncoated characterised in that the sheet comprises: (a) a first coating on at least one surface thereof to aid printability thereon; (b) a second coating comprising an adhesive dispersible in an aqueous medium; and (c) optionally a third coating to modify water permeability through the sheet. The labels are to be applied to articles such as glass containers. Preferred labels are wet glue cellulose labels for example where the first coating also comprises a copolymer of vinyl chloride and vinyl acetate to aid water permeability and hence rapid drying of the label on an article.

FIELD

The present invention relates to the field of labels especially labelsmade from biopolymers used with aqueous adhesives.

BACKGROUND

Labels have been conventionally fixed onto an article with pressuresensitive adhesives in the case of thermoplastic films (such aspolyolefins, e.g. biaxially oriented polypropylene-BOPP) and an adhesivedispersed in an aqueous medium in the case of paper. The latter areoften referred to as wet glue labels but can also be called cold glue orjust glue labels.

The market for alcoholic beverages such as beer, wine or spirits is moreand more competitive and breweries need to find ways of capturing theiraudience and enticing them to purchase their product. Packaging is amajor part of the promotional mix especially at point of sale insupermarkets and the drive for differentiation amongst the manufacturersis furious.

The ‘no-label’ look came into fashion in the pressure sensitive (PS)market several years ago and retailers have found many advantages fromthis new form of shelf appeal. This is achieved by applying a cleartransparent label to the article (or a coloured transparent labelmatched to the colour of the article). As an alternative or as well atransparent or clear label can be coated (e.g. printed or metallised)completely or partially on its reverse side (i.e. the “interior” side tobe adhered to the article) so that such a coat or printing is betterprotected from wear and tear (rubbing, attack by solvents etc) as it isnot on the exterior of the article.

However due to the process used to apply a wet glue label, theconventional transparent plastic films (OPP, polyester-PE, polyethylenephthalate-PET) currently used in the PS market have variousdisadvantages when used as the substrate to produce a transparent wetglue label. The properties of these thermoplastic films are differentfrom the paper labels used on conventional wet glue machines. Forexample thermoplastic films have a high barrier to moisture (they arenot semi-permeable to water) and this causes a wet glue to take muchlonger to dry (and hence the label to fix in place) which can bedisadvantageous on a high speed labelling line or where precise locationof the label is required. Thus thermoplastic films are not an idealreplacement for a paper label on a conventional production line set upto apply a wet glue label to an article such as a bottle. Aqueouscoatings are also not easily compatible with and do not adhere well tosuch thermoplastic films which are often hydrophobic without furthersurface treatments.

The substrate conventionally used to prepare wet glue labels is paperwhich is not transparent. Thermoplastic films are transparent butbecause of the previous stated disadvantages with thermoplastic filmsand wet glue coatings, it has been necessary to use pressure sensitiveadhesives to provide an article with a no look label having acceptableperformance. Thus manufactures currently using labelling equipment forpaper wet glue labels are faced with a significant capital outlay anddisruption to change the to equipment compatible with pressure sensitivelabels if they wish to move to no-look labelling.

Certain water based adhesive systems have been developed for use withlabels.

WO 97/00298 (Henkel) discloses an adhesive system for gluing all-aroundplastic labels onto plastic bodies. The adhesive system has a pick-upglue and an overlapping glue. It is characterised in that the pick-upglue has a sufficient wet gluing power in the wet state and does notadhere to at least one of the substrates in the dried state. The pick-upglue contains 5 to 85% by weight of at least one water-soluble polymerbased on casein, starch, dextrin, glucose, polyvinyl alcohol,polyurethane or polyacrylic acid, 0 to 1.0% by weight of at least oneanti-foaming agent, and 0 to 1.0% by weight of at least onepreservative, the remaining percentage being water.

U.S. Pat. Nos. 4,464,202 and 4,462,838 (both Henkel) describes anaqueous adhesive compositions useful for labeling bottles Moreparticularly, these inventions relate to aqueous adhesive compositionsfor mechanical labeling based upon starch derivatives and having acontent of flow-regulating additives and, optionally, other customaryadditives such as: (a) at least one hydroxyalkyl ether of oxidizedstarch with a mean degree of substitution (MS) of 0.2, together with (b)at least one polymer dissolved in the aqueous phase, the polymer beingselected from the group consisting of water-soluble cellulosederivatives, water-soluble synthetic polymers, casein, and water-solublestarch derivatives different from component (a).

U.S. Pat. No. 4,675,351 (Borden Inc.) describes an adhesive formulationuseful for applying a paper label to a glass bottle, having the tack andrheology making it suitable for use in modern labeling equipment, andimparting water immersion resistance in ice water for a period of atleast 72 hours, which it based on soy protein isolation and does not usecasein.

U.S. Pat. No. 5,455,066 (Henkel) describes a water-containing adhesiveuseful for labelling bottles. The adhesive is based on casein,water-soluble extenders, natural or synthetic resin acids, resinalcohols or resin esters, and an alcohol.

Other non-aqueous adhesives systems have been developed for use withpolymer labels.

U.S. Pat. No. 5,366,251 (Brandt) describes a clear acrylic coated labelwhich is used to provide a reverse side printed water-proof label. Aheat activated solvent based adhesive system is used to bind the film tothe article such as a glass container.

DETAILED DESCRIPTION

The applicant has found that when wet glue was applied directly toconventional OPP label film, the adhesive took days if not weeks to dry.Such poor performance makes wet glues unsuitable for use directly onhydrophobic untreated OPP film. It has been attempted to modify suchhydrophobic plastic polymeric films to make them suitable for use aslabels fixed with a wet glue adhesive. However such techniques are verydifferent from those required to use wet glue with biopolymeric films.

WO 97/43744 (Nordenia) describes an adhesive label consisting of awater-soluble layered plastic film fully or partially coated on itsadhesive side with a dry layer of adhesive made of polyvinyl alcohol,polyvinyl acetate or adhesive based on starch, cellulose, glucose, ordextrin.

The adhesive is activated by moistening the label with water. Afterdrying, the adhesive layer can be removed residue-free from the outerside of the container.

WO 99/19412 (Process Resources Corp.) (=U.S. Pat. No. 6,306,242(Dronzek)) describes a method of fixing polypropylene labels to glass ormetal articles with a water based adhesive. The hydrophobic PP must becoated with a hydrophilic coating to make the film compatible with thewet glue. Such a method is incompatible with conventional equipment usedwith paper labels.

WO 01/56893 (Grafiche Record SRL) describes a method of fixing apolypropylene (PP) label to an article with a water based adhesive (wetglue). Although the method is designed for use with conventional paperlabel equipment, the PP film must coated with acrylic polymers, printedwith inks comprising oxidising salts and then overpainted with a coathaving a specific terpolymer therein to receive the wet glue. This is anexpensive and complicated process.

Thus it is desirable to provide an improved label and process for makingsaid label which solves some or all of the problems described herein andfor example can be used with the well known labelling equipment used toapply paper wet glue labels, can dry in situ in a reasonable timewithout the need to use exotic coatings, yet retains the advantagesassociated with a label of a polymeric film, such as transparency toachieve a no-label look or a protected coat (e.g. metallisation orprinting) on the interior face of the label.

Therefore broadly in accordance with the present invention there isprovided a label comprising a self supporting sheet of a biopolymer,said sheet being substantially transparent to visible light whenuncoated characterised in that the sheet comprises:

(a) a first coating on at least one surface thereof to aid printabilitythereon;

(b) a second coating comprising an adhesive dispersible in an aqueousmedium; and

(c) optionally a third coating to modify water permeability through thesheet.

As defined herein biopolymer excludes paper which of course is nottransparent and is arguably is also non-polymeric.

The terms first, second and third coating and first, second and thirdcomposition as used herein are synonymous.

Preferably the first (printable) coating is applied to only one side ofthe film—the reverse side which is to be adhered to the article—and thenis printed thereon before the adhesive is applied.

Preferably the second (adhesive) coating is applied to only one side ofthe film on top of the other coatings. Optionally the second coating isdried thereon so that the aqueous adhesive becomes active once thesecond coating is re-moistened.

Preferably the third coating of the film modifies the water permeabilitythereof into an optimal tailored range. The film water vapourtransmission rate (WVTR) of the label must not so high (e.g. uncoatedcellulose film) that water evaporates through the film too fast so thewet glue on the reverse side dries too quickly so that the glue becausetoo tacky before there is time to allow the label to be correctlypositioned onto the article by a conventional paper label machine.

Yet the WVTR of the label must not be too low (such as uncoated OPPfilm) that the adhesive dries too slowly so the label is not properlyfixed onto the article and can slide around on its surface on a cushionof liquid adhesive. To achieve the optimal WVTR a third coating may beapplied to both sides of the film.

The first (printable) coating and second (aqueous adhesive) coating maybe applied to opposite surfaces of the film label (i.e. to define anadhesive side and a printed side).

Preferably the first (printable) coating and the third (waterpermeability modifying) coating may be the same or may be combined sothe printable coating may also modify the water permeability of the filmas desired. More preferably the first and third coatings (optionally thecombined as the same composition) may be applied to at least one side ofthe film, most preferably to both sides of the film to form a two sidecoated film printable on both sides and with optimal water permeability.

The second and third coatings may also be applied to the same side ofthe film, both sides of the film or different sides. Similarly thesecond and third composition may be the same or may be combined so theaqueous adhesive may also modify water permeability of the film asdesired.

Thus the first, second and third coatings may comprise the same and/ordifferent compositions and may be applied to either or both surfaces ofthe film simultaneously and/or sequentially. A further purpose of thefirst and/or third coatings added to the reverse side of the film is toaid adhesive anchorage of the second adhesive coat.

It is also possible that the films of the present invention my be coatedor printed with a further non-transparent coat or layer (e.g. ametallised coat) on the side of the film which in use is to be stuckonto the article with the wet glue. In this manner the coating orprinting is seen through the transparent film but is protected fromexternal wear. It is even possible that the initially clear ortransparent biopolymer film is weakly opaque such that some of a reverseside design can be seen through the label and/or through the other sideof the article (e.g. in a bottle through its contents on the interiorside of the label).

Conveniently the thickness of the second coating (calculated from theunits of g per m²) is at least about 10 g per m², preferably 20 g perm², more preferably from about 30 g per m² to about 40 g per m², mostpreferably about 33 g per m² to about 35 g per m². These values arecalculated from the wet value of the liquid coating when applied. Afterdrying the dry-coat weight is typically 50% that of the wet coat weight.

The biopolymer may be a single sheet or form part of a laminate,preferably the label is either 1 or 2 ply. The advantage of a two ply orduplex structure is that it has improved wet strength for wet glue labelapplications. Without being bound by any theory it is believed that thestructure of a single layer biopolymeric film such as a regeneratedcellulosic film can be divided into surface regions (at each of the twosides of the film) which are less absorbent to liquid (analogous to aloufa) and an inner or core region more absorbent to liquid (analogousto a sponge). A duplex film is formed by adhering two webs of a singlelayer film together e.g. by laminating them together in a drier. Aduplex biopolymer film has four skin and two core layers compared to asingle ply film with has two skin layers and one core, and this isbelieved to be the mechanism for improved wet strength of duplex filmswhich are especially preferred for use to make the labels of the presentinvention.

The biopolymers which may be used to form (or which substantiallycomprise of the present invention may be obtained and/or obtainable froma biological (preferably plant and/or microbial) source and may comprisethose organic polymers which comprise substantially carbon, oxygen andhydrogen. Conveniently biopolymers may be selected from carbohydrates;polysaccharides (such as starch, cellulose, glycogen, hemi-cellulose,chitin, fructan inulin; lignin and/or pectic substances); gums;proteins, optionally cereal, vegetable and/or animal proteins (such asgluten [e.g. from wheat], whey protein, and/or gelatin); colloids (suchas hydro-colloids, for example natural hydrocolloids, e.g. gums); otherpolyorganic acids (such as polylactic acid and/or polygalactic acid)effective mixtures thereat and/or effective modified derivativesthereof.

Further details of each of the biopolymers which may be used to formfilms of the invention are given below.

Starch may comprises native and/or modified starch obtained and/orobtainable from one or more plant(s); may be a starch, starch-ether,starch-ester and/or oxidised starch obtained and/or obtainable from oneor more root(s), tuber(s) and/or cereal(s) such as those obtained and/orobtainable from potato, waxy maize, tapioca and/or rice.

Gluten may comprise a mixture of two proteins, gliadin and gluteninwhose amino acid composition may vary although glutamic acid and pralineusually predominate.

Gums are natural hydro-colloids which may be obtained from plants andare typically insoluble in organic solvents but form gelatinous orsticky solutions with water. Gum resins are mixtures of gums and naturalresins.

As used herein the term carbohydrate will be understood to comprisethose compounds of formula Cx (H₂O)_(y) which may be optionallysubstituted. Carbohydrates may be divided into saccharides (alsoreferred to herein as sugars) which typically may be of low molecularweight and/or sweet taste and/or polysaccharides which typically may beof high molecular weight and/or high complexity.

Polysaccharides comprise any carbohydrates comprising one or moremonosaccharide (simple sugar) units. Homopolysaccharides comprise onlyone type of monosaccharide and heteropolysaccharides comprise two ormore different types of sugar. Long chain polysaccharides may havemolecular weights of up to several million daltons and are often highlybranched, examples of these polysaccharides comprise starch, glycogenand cellulose.

Polysaccharides also include the more simple disaccharide sugars,trisaccharide sugars and/or dextrins (e.g. maltodextrin and/orcyclodextrin).

Polysaccharides may comprise a polymer of at least twenty or moremonosaccharide units and more preferably have a molecular weight (M_(w))of above about 5000 daltons. Less complex polysaccharides comprisedisaccharide sugars, trisaccharide sugars, maltodextrins and/orcyclodextrins. Complex polysaccharides which may be used as biopolymersto form or comprise films of present invention comprise one or more ofthe following: Starch (which occurs widely in plants) may comprisevarious proportions of two polymers derived from glucose: amylose(comprising linear chains comprising from about 100 to about 1000 linkedglucose molecules) and amylopectin (comprising highly branched chains ofglucose molecules).

Glycogen (also known as animal starch) comprises a highly branchedpolymer of glucose which can occur in animal tissues.

Cellulose comprises a long unbranched chain of glucose units.

Chitin comprises chains of N-acetyl-D-glucosamine (a derivative ofglucose) and is structurally very similar to cellulose.

Fructans comprise polysaccharides derived from fructose which may bestored in certain plants.

Inulin comprises a polysaccharide made from fructose which may be storedin the roots or tubers of many plants.

Lignin comprises a complex organic polymer that may be deposited withinthe cellulose of plant cell walls to provide rigidity.

Pectic substances such as pectin comprise polysaccharides made upprimarily of sugar acids which may be important constituents of plantcell walls. Normally they exist in an insoluble form, but may changeinto a soluble form (e.g. during ripening of a plant).

Polylactic and/or polygalactic polymers and the like comprise thosepolymeric chains and/or cross-linked polymeric networks which areobtained from, obtainable from and/or comprise: polylactic acid;polygalactic acid and/or similar polymers and which may be madesynthetically and/or sourced naturally.

Other types of polysaccharide derivatives one or more of which may alsobe used to form (in whole or in part) films of the present invention maycomprise any effective derivative of any suitable polysaccharide (suchas those described herein) for example those derivatives selected fromamino derivatives, ester derivatives (such as phosphate esters) etherderivatives; and/or oxidised derivatives (e.g. acids).

Preferred biopolymer films are those formed from a biopolymer selectedfrom cellulose, cellulose derivatives (such as cellulose acetate) and/orpolylactic acid.

More preferred films comprise cellulose which is substantiallycontinuous, more preferably non-woven and/or entangled, in structure.Most preferably the film of the invention comprises non-microbialcellulose such as cellulose regenerated from a cellulosic dispersion ina non-solvating fluid (such as but not limited to NMMO and/or a mixtureof LiCl and DMP). One specific example is “viscose” which is sodiumcellulose xanthate in caustic soda. Cellulose from a dispersion can becast into film by regenerating the cellulose in situ by a suitabletreatment (e.g. addition of suitable reagent which for viscose can bedilute sulphuric acid) and optionally extruding the cellulose thusformed. Such cellulose is known herein as regenerated cellulose andpreferred films of the present invention comprise regenerated cellulose.

Conveniently films of the present invention substantially comprisecellulose from a wood source, most preferably at least 90% of thecellulosic material is from a wood source.

Preferably the first coating is applied to aid printability and also tohelp to control evaporation rate of the water from the glue (first coatalso acts as the third coating) once the label has been applied to anarticle. More preferably (and like the biopolymer substrate) thefirst/third coating is semi-permeable. This enables the second coatingof the aqueous adhesive composition to dry sufficiently quickly to setthe label in position on to the bottle. If the moisture barrier of thecombined first/third coating is too good the drying time is extended,which increases the chance of the label moving and finally drying in thewrong place.

The first coating comprises component(s) which are receptive to printinginks and/or as the anchor of an ink to the label surface. The secondcoating (wet label adhesive) may comprise any suitable adhesive which isdispersible in an aqueous medium, for example casein adhesive, whichcontains 50% water.

The third coating comprises a component to control water permeability,preferably comprising a ethylenic (co)polymer substituted byelectronegative groups, more preferably a (co)polymer of vinyl chloride,acrylic, vinyl acetate, polyester and: or isocyanate monomers, mostpreferably the coating is substantially free of chlorine containingspecies. Most preferred components of a combined first (printable) andthird (WVP) coating are chlorine-free acrylic, polyesters andpolyurethanes.

Labels of the invention may be coated on one side or two sides of thefilm, although two side coated labels are preferred. Two side coatedfilms are more stable and are less prone to problems such as wrinklingor creasing, so producing labels of greater aesthetic appeal.

Any of the first, second and/or third coating may also comprise waxesand other conventional additives as required to modify the slip andblock resistance of the coating.

Such additives may be selected from one or more of the following and/ormixtures thereof fatty acids e.g. Behenic Acid; fatty acid ester amide(amide wax) e.g. that available commercially under the trade name Lancowax E2S; hydrogenated castor oil mono and diesters of phosphoric acide.g. that available commercially under the trade name Crodafos S2;maleic acids; similar acids and/or ester, and/or salts thereof and/orother simple derivatives thereof; and/or inorganic materials such asclays e.g. china clay.

Preferably the biopolymer wet glue labels of the present inventionfurther exhibit at least one of the following advantageous properties.

Due to the inherent properties of biopolymer (preferably cellulose)film, the film may swell when exposed to water and will definitelyshrink to less than its original measurements when dried after wetting.Thus when adhesive is being applied to an article (such as a containere.g. a bottle) the label may swell, but after it has been applied to thearticle the label will shrink whilst drying and form a tighter bondaround the article.

Because of the permeability of biopolymers especially cellulose, theadhesive can dry within a reasonable time similar to paper and so theselabels can be used as drop in replacements for paper wet glue labels.

A coated labels have good anchorage of inks and readily allow uptake ofwater by the biopolymer. When dry preferred labels of the invention drysmoothly onto the surface of the article.

Because of the permeable nature of the biopolymer the labels of theinvention have the ability to be washed off and the article (e.g.bottle) can be more easily re-used. This is particular important in somecountries such as Germany and Finland.

Labels formed from cellulose in particular have good slip and antistaticproperties which are required for ease of sheet feeding and cut andstack processing of labels. This is inherent in cellulose film.

Water permeability herein may be measured in standard test BS 3177 at37° C. and 75% relative humidity (RH). Conveniently the water vapourpermeability is from about 10 to about 1000 g per m² per 24 hours; moreconveniently from about 50 to about 600 g per m² per 24 hours.Preferably the water permeability of the film is from about 100 to about400 g/m² d, more preferably from about 150 to about 300 g/m² d, mostpreferably from about 200 to about 250 g/m² d; for example about 210g/m². Alternatively or as well the as water permeability, the watervapour transmission rate (WVTR) of the films herein may be measured instandard test ASTM E 96 at 37° C. and 30% relative humidity (RH) usingthe water method for the dry film and the inverted water method for thewet film. Preferably the WVTR of the dry film is as given above forwater permeability.

When measured the wet film may show from about 5 to about 15 fold,preferably from about 5 to about 8 fold higher WVTR than the same filmwhen dry.

Preferably the film further comprises a plasticiser, more preferably inan amount from about 10% to about 30%, most preferably about 20% byweight of the cellulose film. The plasticiser may be any suitablematerial which is compatible with food packaging (for example is foodcontact approved) and/or substantially non-toxic in the amounts used.For example the plasticiser may be selected from glycols, (such as MPG,TEG, PEG), urea, sorbitol, glycerol and/or mixtures thereof in anysuitable mixtures and ratios to those skilled in the art. For exampleone suitable plasticiser may comprise such as a mixture of sorbitol andglycerol in the respective weight ratio of 60:40 by weight of solids.

Since the cellulose film is strong and inert, if necessary it can besterilised in any convenient way. It may be stored at any temperature,and does not require special conditions. It is of unlimited durability.The film has determined permeability to liquids and air, acharacteristic molecular weight and structure, a predictable thicknesswhen dehydrated, in addition to other specific physical characteristics.

The cellulosic film may comprise other conventional film additivesand/or coatings well known in the art of film making such as those whichare compatible with packaging, preferably food packaging and morepreferably are food contact approval by the FDA in the US (and/oranalogous agencies in other countries). Such additives and/or coatingsmay comprise softeners, anti-static agents, particulate additives and/ormay be tinted or otherwise treated, for example impregnated with one ormore other active ingredients, provided such modifications arecompatible with the uses of the film as a label as described herein.

The average thickness of a film of the present invention may be up toabout 2 mm (e.g. if a foamed film is used), preferably up to about 50microns before incorporation of the particulate additives. Morepreferably the average thickness of a film of the present invention isfrom about 20 to about 45 microns, most preferably from about 20 toabout 30 microns. Preferred films used in the present invention areduplex laminated films (i.e. where a single web is laminated ontoitself) to provide the improved stiffness desirable in a label.

In a further aspect of the present invention, broadly there comprises amethod for preparing and/or applying a label, the method comprising thesteps of

(a) coating a biopolymeric sheet on at least one surface thereof with anaqueous composition with an adhesive dispersed therein;

(b) treating at least the opposite surface of the sheet, optionally bothsurfaces, to improve its printability,

(c) drying the film to remove excess water;

(d) applying the label to an article; and

(e) optionally drying the article to affix the label thereon.

Any suitable methods of making a biopolymer may be used preferably acellulose film, more preferably made by a regenerated method. A mostpreferred method is the well known viscose method for preparingcellulose film in which case the particles are added to the viscose.

Many other variations and the details of construction and compositionwill be apparent to those skilled in the art and such variations arecontemplated within the broad scope of the present invention.

One aspect of the invention is the use of a film of the presentinvention to form a label as described herein.

Another aspect of the invention is the use of a cellulosic film of thepresent invention to fix a label to an article.

Further aspects of the invention and preferred features thereof aregiven in the claims herein.

It will be appreciated that although the films of the present inventionare primarily designed for use in the field of labels for customerarticles, especially food and beverages, more especially alcoholicbeverages such as spirits, but they could be used in other applicationswhere similar film properties are desired.

Forming Viscose

Wood pulp (usually as sheets) was added to a caustic soda (NaOH)solution containing a manganese (e.g. MnSO₄) catalyst mixed therein. Themixture was agitated to form a slurry which was fed through a presswhere it was compressed to produce a continuous mat of alkali-cellulosewhich was conveyed to a shredding machine and broken into crumbs. Thecrumbs were slowly fed by a large conveyer belt through a controlledhumidified atmosphere to be chemically aged. Without wishing to be boundby any mechanism it is believed that the structure of large cross-linkedlignin wood fibres in the pulp was oxidised by the NaOH (with the helpof the MnSO₄ catalyst) to be chemically broken down into smaller sized(micron-sized) particles. The aged alkali cellulose mixture was cooledto ambient temperature and added to a pressure vessel. Carbon disulphidewas then added to the alkali-cellulose under reduced pressure and themixture turned from white to orange yellow as sodium cellulose xanthatewas formed. A measured amount of weak caustic soda solution was added tothe mixture, which was agitated until it became a thick orange liquid(also known as unripe viscose). The unripe viscose was homogenised,filtered, deaerated and filtered once more to form a clean clear liquid(also known as pure viscose) which was cast into a highly transparent,flexible cellulose film as described below. It will also be appreciatedthat if coloured or opaque cellulose film was desired suitable colorantsand/or opacifiers may also be added to the pure viscose before castingthe film as well as any other compatible and suitable ingredients whichit is desired to incorporate throughout the film.

Casting Film

Viscose (formed as described above) was extruded under pressure througha jet into a bath of dilute sulphuric acid to regenerate a continuousweb of cellulose film. The film web which was initially opaque andflimsy was passed in succession through various baths (e.g. of acid,water, soda sulphide, water, bleach, water and softener) and over manyrollers (typically over 250) to remove impurities, recover carbondisulphide and/or wash the web so the final film produced had thedesired strength and flexibility. When the web of wet cellulose filmpassed from the final bath it was dried in hot air to remove excesswater and then conditioned in moist air (to control the correct amountof water content in the final film to ensure its optimal properties).The film web may be optionally treated (e.g. by a corona discharge) toprovide an anchor to chemically bond with further optional coatings andthen the web was wound onto a roller to produce a finished cast roll ofregenerated cellulose film. Depending on the desired end-use thecellulose film may be used without further treatment and/or coatings.

These cellulose films used in the labels of the invention have manyother well known useful properties such as one or more of the following:excellent barrier to gas (e.g. to oxygen), water permeablility (thedegree of which can be tailored by the process by which it is made);semi-permeability (for example as a membrane for dialytic and/or osmoticprocesses); non-fusable core (i.e. film does not melt); natural deadfold, ease of opening, compressibility and compactibility as waste,biodegradeablility and composability, anti-static, high transparency andhigh gloss.

Coating Film

To improve as appropriate certain properties of the cellulose film suchas moisture resistance, heat sealability, and/or machineability,optionally one or both sides of the film may be coated with one or morecoatings which may for example be applied from a solvent and/or aqueousdispersion. Suitable coatings may include any which are suitable for theintended use such as conventional nitrocellulose, vinyl chloride and/orvinyl actetate coatings.

Preferred coatings which are suitable for use with cellulose films usedas labels with wet glue adhesives include coatings which do not containchlorine, such as those based on chlorine-free polymers for exampleacrylic, polyurethanes, polyesters, polyvinyl alcohols and/or anysuitable mixtures or copolymers thereof.

Coatings may be applied at the end of a casting machine or within a hightower as appropriate.

In a coating tower the cellulose film web was immersed in a lacquer bathand excess lacquer was removed by doctor rollers. The lacquer was thensmoothed by reverse smoothing rollers and any excess solvents wereremoved from the lacquer in a vertical drier and may be recovered. Theweb of film left the drier at the head roll and descended to groundlevel through a conditioner that restored the moisture lost during theduring the coating and drying process. After being passed over chillrollers the coated film was wound back onto mill rolls. Coatings mayalso be applied to the film by spraying onto the web within a solventtower rather than passing the web through a lacquer bath.

The present invention will now be described in detail with reference tothe following non limiting example which is by way of illustration only.

Example 1

A production machine was set up in a conventional manner to produceregenerated cellulose film from the well known viscose method asdescribed herein. The viscose used had a cellulose content of 9.3% andthe resultant film had a substance of 30 grams per square meter.

One side of the film can be treated with a corona discharge and thenprinted. The reverse side of the film can be coated with a conventionalcoating of vinyl chloride/vinyl acetate copolymer at a coat weight of 60g per m². A standard wet glue caesin adhesive (50% water) can then beapplied to the same side as the copolymer.

The label can then be directly applied to a bottle in a conventional wayusing unmodified (or only trivially modified) conventional labelingequipment set up for wet glue paper labels, to achieve a transparentprinted label which dried rapidly on the bottle without significantwrinkling or misalignment of the label position to provide an acceptableclear look label on the bottle.

Example 2

A coating formulation was prepared (weights based on 100 parts ofpolymer) by mixing the following ingredients.

Trade Name Chemical Type Amount w/w Polymers Hostaflex CM131 PVC/PVAcopolymer 80 Ixan PNE 613 PVdC copolymer 20 Waxes Behenic Acid Fattyacid 1.5 Distec Hydrogenated Castor Oil 0.17 Crodafos S2 Mono and Diesters of Phosphoric acid 0.27 Lanco Wax E2S fatty acid ester amide(amide wax) 0.5 Others Maleic acid- 1.2 Infilm 1735 China Clay 0.8

Two webs of a regenerated cellulose film were laminated together oncasting machine dryers. This helped to give stiffness and stability tothe film. The weight of this base film was 62 g/m² (43 micronsthickness). The laminated film was then coated in a conventional mannerwith a solvent lacquer of the above copolymer coating formulation onboth sides of the film (two side coating) to give after drying asemi-permeable moisture barrier on both sides of the film. The finalweight of the film was 64.5 g/m² (45 microns thickness).

The permeability of this coated film (measured in standard test ASTM E96 at 38° C. and 90% relative humidity) was 370 g/m² day.

Other properties tested for the film of Example 2 are now given withtest method indicated. All these tests were carried at 23° C.±2° and 50%RH unless indicated.

Optical gloss at 45° was 95% (ASTM D 247); wide angle haze at 2.5° was4% (ASTM D 1003); coefficient of friction (film to film) static was0.25, dynamic was 0.20 (ASTM D 1894); mechanical data (ASTM D882)-tensile strength was 162 NMm⁻² (MD) & 95 NMm⁻² (TD); elongation atbreak was 20% (MD) & 55% (TD) and elasticity modulus (1% Secant)was >3000 NMm⁻² (MD) & >1500 NMm⁻² (TD); temperature flexibility rangewas from 0° C. to 290° C.

This two sided coated film was then applied as a label film to a bottleusing a conventional wet glue adhesive of 50% caesin water applied toone side of the label film at the point of application. The label may beprinted and/or metallised or otherwise coated before application of thewet glue on the adhesive side of the film so the print or metallisationis seen through the transparent cellulose film yet is protected formwear etc by the transparent film.

The above films have the following advantages for use as a label with awet glue adhesive: excellent clarity for a “no-label” look; excellentprintability using traditional printing methods; excellent adsorptionand fast drying of the adhesive; anti-static and excellent slipproperties; resistant to oils and greases; high stiffness forconversion; high gloss and a biodegradable base film.

1. A transparent label comprising a self supporting transparentbiopolymer film, said film being substantially transparent to visiblelight wherein the film comprises: (a) a first transparent printablecoating on at least one surface thereof to aid printability thereon,said first coating being semi-permeable and comprising at least onecomponent which is receptive to printing inks; (b) a second transparentcoating comprising an adhesive dispersible in an aqueous medium; and (c)optionally a third transparent semi-permeable coating to modify waterpermeability through the film, wherein said label has a waterpermeability of from about 50 to about 600 g/m² day, measured instandard test ASTM E 96 at 38° C. and 90% relative humidity.
 2. A labelas claimed in claim 1, in which the first coating and the third coatingare the same.
 3. A label as claimed in claim 2, in which the film iscoated on both surfaces with the combined first and third coating.
 4. Alabel as claimed in claim 1, having a water permeability of from about100 to about 400 g/m² day.
 5. A label as claimed in claim 1, in whichthe biopolymer film comprises film made from cellulose, a cellulosederivative and/or polylactic acid.
 6. A label as claimed in claim 1, inwhich the biopolymer film is a two layer laminate.
 7. A label as claimedin claim 1, wherein said label has 1% Secant elasticity modulus of atleast about 2000 NMm⁻² in the machine direction of the biopolymer filmwherein said 1% Secant elasticity modulus is measured in standard testof ASTM D
 882. 8. A label as claimed in claim 1, which further comprisesa metallised layer on the reverse surface of the film, the layer beinglocated between biopolymer film, and optionally on top of any firstand/or third coatings thereon and the second adhesive layer.
 9. A labelas claimed in claim 1, wherein said label has 1% Secant elasticitymodulus of at least about 1000 NMm⁻² in the transverse direction of thebiopolymer film, wherein said 1% Secant elasticity modulus is measuredin standard test of ASTM D
 882. 10. A label facestock comprising a labelas claimed in claim 1 adjacent a release liner.
 11. A transparent labelcomprising a self supporting transparent biopolymer film having athickness from about 20 to about 45 microns, said film beingsubstantially transparent to visible light wherein the film comprises:(a) a first transparent printable coating on at least one surfacethereof to aid printability thereon, said first coating beingsemi-permeable and comprising at least one component which is receptiveto printing inks; and (b) a second transparent coating comprising anadhesive dispersible in an aqueous medium; wherein said label has 1%Secant elasticity modulus of at least about 1000 NMm⁻² in the transversedirection of the biopolymer film, wherein said 1% Secant elasticitymodulus is measured in standard test of ASTM D
 882. 12. The transparentlabel of claim 11, wherein the film further comprises a thirdtransparent semi-permeable coating to modify water permeability throughthe film.
 13. The transparent label of claim 11, having a waterpermeability of from about 100 to about 400 g/m² day.
 14. Thetransparent label of claim 11, wherein the biopolymer film comprises afilm made from cellulose, a cellulose derivative and/or polylactic acid.15. A transparent label comprising a self supporting transparentbiopolymer film, said film being substantially transparent to visiblelight wherein the film comprises: (a) a first transparent printablecoating on at least one surface thereof to aid printability thereon,said first coating being semi-permeable and comprising at least onecomponent which is receptive to printing inks; (b) a second transparentcoating comprising an adhesive dispersible in an aqueous medium; and (c)optionally a third transparent semi-permeable coating to modify waterpermeability through the film, wherein said label has a waterpermeability of from about 50 to about 600 g/m² day, measured instandard test ASTM E 96 at 38° C. and 90% relative humidity, and whereinsaid label-has 1% Secant elasticity modulus of at least about 2000 NMm⁻²in the machine direction of the biopolymer film wherein said 1% Secantelasticity modulus is measured in standard test of ASTM D 882.